Lecture Notes: ADC and DAC Introduction

Overview

• ADC: Analog to Digital Converter
  • Converts analog signals into digital signals.
• DAC: Digital to Analog Converter
  • Converts digital inputs back into analog signals.
• Common Applications:
  • Music streaming on smartphones (DAC converts digital bit stream to analog for speakers).
  • Phone calls (Microphone converts voice to electrical signal, ADC digitizes it, DAC at receiver converts back to analog).

Importance of ADC and DAC

• Analog Signals: Most signals (temperature, sound, etc.) are analog.
• Noise Susceptibility: Analog signals are more prone to noise, hard to process/store.
• Advantages of Digital Signals:
  • Less noise susceptibility.
  • Easier to process and store.

Signal Conversion Process

• Not Lossless: Information can be lost during conversion.
• Analog Signal Characteristics:
  • Continuous in time and amplitude (infinite resolution).
• Digital Signal Characteristics:
  • Discrete in time and amplitude.

Steps in Analog to Digital Conversion

1. Sampling

   • Process of taking samples of the analog signal at a particular rate.
   • More samples = more accuracy in representing the signal.
   • Nyquist Theorem: Sampling rate must be at least twice the maximum frequency of the signal.
   • Aliasing: Occurs if the sampling rate is less than the Nyquist rate.

2. Quantization

   • Assigning a sampled signal a specific value from a finite set of values (
   • E.g., 16 levels for quantization).
   • Resolution: Number of bits used determines how close the quantized value is to the actual value.
   • Quantization Error: Introduced during the quantization process (related to LSB).

3. Encoding

   • Converting quantized values into a binary format.

Resolution and Quantization

• The resolution is defined in bits (n bits = 2^n discrete levels).
• Example: For a 3-bit ADC with 10V full scale range:
  • Resolution = 10V / 2^3 = 1.25V minimum change detectable.
• Trade-off in resolution and range: Increasing reference voltage reduces conversion range.

Sampling Process and Anti-aliasing

• Sample and Hold Circuit: Holds the signal constant during quantization.
• Anti-aliasing Filter: Low-pass filter used to remove high-frequency components before sampling.

Digital to Analog Conversion (DAC)

• Converts digital bitstream back into analog signals.
• Resolution impacts the accuracy of the reconstructed signal.
• Important parameters: Resolution, reference voltage, settling time.

Key Parameters for ADC and DAC

• Gain and offset error.
• Non-linearity.
• Total harmonic distortion.

Types of ADCs and DACs

• Different designs offer various advantages (resolution vs conversion speed).
• Upcoming videos will cover types of ADCs and DACs in detail.

Conclusion

• Understanding ADC and DAC is essential in electronics for signal processing.
• Open to questions and feedback in the comments.
• Encouragement to like and subscribe for more videos.